Optical sensors for sensing objects with the aid of light have been used so far in a variety of applications. Examples of those optical sensors are disclosed in Patent Literatures (PTLs) 1 and 2.
PTL 1 discloses a measurement method for use in a measuring device including a measuring chip and a reference chip, and utilizing attenuated total reflectance. In the disclosed measurement method, a sensitivity difference between the measuring chip and the reference chip is obtained with photodiodes (detection units) that are included respectively in the measuring chip and the reference chip. Then, an analyte is added to only the measuring chip, a measurement result of the reference chip is calibrated with the above-mentioned sensitivity difference, and a measurement result of the measuring chip is corrected with the calibrated measurement result. This method measures a concentration of the analyte (object) by evaluating a change in the attenuated total reflectance.
PTL 2 discloses a molecule detector including a light source that emits light of a predetermined wavelength, an optical element including a waveguide (core layer) of a photonic crystal structure having changeable optical characteristics, and a detection unit that detects adsorption of a specific molecule on the basis of a change in light emitted from the optical element. A concentration of the specific molecule (object) adsorbed on the waveguide is measured by the detection unit evaluating a change in the optical characteristics of the waveguide. Furthermore, in the disclosed molecule detector, when there are plural waveguides, the above-mentioned measurement can be performed free from influences of environmental changes, etc. by employing any one of the waveguides as a reference.